Electric pipe heater



July 18, 1967 J. E. 5mm 3,331,946

ELECTRIC PIPE HEATER Filed 001;. 8, 1964 l/CY/YYQJ f. [SO/bro mvsmonATTORNEVJ United States Patent 3,331,946 ELECTRIC PIPE HEATER James E.Bilbro, Houston, Tex., assignor to Thermon Manufacturing Co., acorporation of Texas Filed Oct. 8, 1964, Ser. No. 402,543 2 Claims. (Cl.219535) ABSTRACT OF THE DISCLOSURE Heat transfer apparatus including achannel member with heat transfer material disposed therein prior tomounting on a pipe or similar structure, wherein a heat conductorelement is disposed in the heat transfer material without air gaps andthe entire assembly is clamped on the pipe for improving the transfer ofheat between the heat conductor element and the pipe.

Background of the invention In United States Patent No. 2,982,992, anapplicator apparatus for applying heat transfer material in a puttylikeor plastic condition is disclosed.

Summary of the invention The present invention includes a heat transfermaterial which is preformed in a channel member and which improves heattransfer rather than serving as an insulator. A heat conductor elementor elements such as electrical resistance wires are embedded in the heattransfer material. The channel member is clamped onto the pipe so thatits longitudinal edges engage the external surface of the pipe, wherebythe heat transfer material and heat conductor element are confined toprevent a loss of the heat transfer material and the formation of airgaps in such material during the use of the apparatus.

It is therefore an object of this invention to provide an applicator forheat transfer material which is an improvement on the apparatus ofUnited States Patent No. 2,982,- 992 in that it is prefabricated so asto facilitate application of the heat transfer material and so as toprovide an improved final installation of such material.

An important object of this invention islto provide a new and improvedheat transfer apparatus which is adapted to apply an evenly distributedcovering of a heat transfer material on electrical heating wires, steamtracing, and the like whereby gaps in such material are avoided.

Another object of this invention is to provide a new and improved heattransfer apparatus which is adapted to apply the heat transfer materialin a plastic condition and which may be immediately used afterinstallation without delaying for a curing or solidifying of the heattransfer material.

A particular object of this invention is to provide a new and improvedheat transfer apparatus wherein heat transfer material in a plasticcondition is packaged in a channel member and is adapted to be pressedover a heating and/ or cooling element or elements and thereaftersecured by bands or other holding means to a pipe, plate or other objectto be heated or cooled by the heating and/ or cooling element orelements, whereby an installation is obtained in which no air spaces orgaps in the heat transfer material occur.

A specific object of this invention is to provide a new and improvedheat transfer apparatus wherein electrical heating wires are embedded ina heat transfer material which is confined on an object by a channelmember.

Still another object of this invention is to provide a new and improvedprefabricated package for heat transfer material and applicator whereina pair of applicators are assembled together, and wherein the heattransfer material is protected from contamination.

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The preferred embodiment of this invention will be describedhereinafter, together with other features thereof, and additionalobjects will become evident from such description.

The invention will be more readily understood from a reading of thefollowing specification and by reference to the accompanying drawingsforming a part thereof, where in an example of the invention is shown,and wherein:

FIG. 1 is a view, partly in elevation and partly in section,illustrating the heat transfer apparatus of this invention when mountedon a pipe for use;

FIG. 2 is a vertical sectional view taken on line 22 of FIG. 1;

FIG. 3 is a vertical sectional view illustrating a package forfacilitating the use of a prefabricated applicator of this invention;

FIG. 4 is a vertical sectional view illustrating a modified shape forthe channel member of the prefabricated applicator of this inventionprior to the insertion of the wires or other heat conductor elementtherein;

FIG. 5 is a view similar to FIG. 4, but illustrating anothermodification of the channel member of the prefabricated applicator ofthis invention;

FIG. 6 is a vertical sectional view similar to FIG. 4, but illustratinga further modification of the shape of the channel member of theprefabricated applicator; and

FIG. 7 is also a vertical sectional view illustrating still anothermodification of the shape of the channel member for the prefabricatedapplicator of this invention.

In the drawings, the letter A designates generally the heat transferapparatus of this invention. Such apparatus A is adapted to be mountedon and secured to an object to be heated or cooled such as indicated bythe pipe P. Briefly, the heat transfer apparatus A includes aprefabricated applicator which is adapted to be positioned over a heatconductor element or elements H, whereby heating or cooling with suchelements H may be effectively accomplished, so as to transfer heat to orfrom fluid or other material within the pipe P or other object to whichthe heat transfer apparatus A is attached.

Considering the invention more in detail, the heat transfer apparatus Aincludes a channel member 10 which is formed of steel, rigid plastic orother relatively rigid material. Such channel member 10 may takenumerous shapes as will be more evident hereinafter, but in eachinstance, the channel member 10 is provided with a longitudinal channelsuch as indicated at 1001 (FIGS. 2 and 3). In the form of the inventionillustrated in FIGS. 1-3, the channel member 10 is semi-cylindrical inshape so that the channel 104: is a convex groove which terminates inlongitudinally extending edges 10b.

The length of the channel member 10 may be substantially the same as thelength of the heat conductor element or elements H, or in someinstances, the channel member 10 may be formed by a plurality ofrelatively short lengths as compared to the length of the element orelements H which are joined together when applied to the pipe P or otherobject to be heated or cooled so as to completely cover that portion ofthe element H extending along the pipe P or other object.

To facilitate the installation of the heat transfer apparatus A on thepipe P or other object, it is preferable to provide a prefabricatedapplicator which includes the channel member 10 and heat transfermaterial 12 disposed therein (FIG. 3). The heat transfer material 12 ispreferably of the type sold under the trademark Thermon, which is amaterial that is in a putty-like state or plastic condition at normalroom temperatures. Such material may be thermosetting and thereforeadapted to harden upon the application of heat, or it may benonhardening. By way of example, such heat transfer material may havethe following components in the percentages by weight indicated:polybutene 50%; 4,4 methylene bis (2,6 di-tert-butylphenol).5% pyrogeniccolloidal silica (sold under the trademark Cab-o-Sil)2.0%; andgraphite47.5%. Various organic binders may be used instead of thepolybutene, such as butyl rubber and uncatalyzed epoxy resin or siliconeand such organic binder may be present in an amount of from about 40 toabout 60% by weight. In place of the 4,4 methylene bis, hydroquinone maybe used, preferably in an amount of about .05 Instead of the graphite,other metals in powdered granular or particulate form, metal oxides orother metallic compounds and any form of divided carbon may be used,either by themselves or in a mixture of one or more of such heatconducting agents.

To facilitate the storage and handling of the prefabricated applicatorof this invention, the package illustrated in FIG. 3 may be employedwherein a pair of such prefabricated applicators is mounted togetherwith the heat transfer material 12 in engagement with a separator strip14 formed of a silicone sheet or a polyethylene sheet or of some similarmaterial which is readily releasable from the heat transfer material 12and the channel members 10. With the package illustrated in FIG. 3, theheat transfer material 12 is protected against contamination by foreignobjects while in storage and is prevented from being exposed until readyfor actual use.

In the preferred embodiment, the heating element or elements H is in theform of a pair of electrical wires 20 and 21 which are preferablycarried as a unit in a layer of insulation or other covering 22.Normally, each of the electrical wires 20 and 21 is provided with asleeve of insulating material and an outer covering of metallic wirebraid is used to form the composite heating element H. Such wire braidis indicated in FIG. 1 at 22.

In any event, in the final installation of the heat transfer apparatusA, the heat conductor element H is embedded in the heat transfermaterial 12 with both disposed on the pipe P or other object to beheated or cooled as best seen in FIGS. 1 and 2. The longitudinal edges bof the channel member 10 rest in contact with the external surface ofthe pipe P or are substantially in contact therewith so that the heattransfer material 12 surrounds the heating element or elements H andeliminates any air spaces between the heating element Hand the pipe P,thereby assuring an effective transfer of heat to or from the heatingelement or elements H to the pipe P and the contents thereof.

The channel .member 10 is secured to the pipe P by longitudinally spacedbands or straps 30 formed of metal or any other material such asplastic. The straps or bands 30 are preferably locked around the pipe Pand the channel member 10 by any type of crimped locking element 31 orother suitable means for accomplishing a locking of the strap or band inthe encircling position to thereby secure the channel member 10 firmlyon the pipe P. In FIG. 1, the locking element 31 is shown with suitablecrimps 31a which are of a conventional construction for clamping bands.

In the use of the form of the invention illustrated in FIGS. 1-3, theprefabricated package shown in FIG. 3 is first assembled for storage ortransportation to the point of use. The length of the channel members 10may vary, as previously pointed out, but normally they will besubstantially co-extensive with the length of the heat conductorelements H which are to be employed therewith. At the point ofinstallation, the heat transfer apparatus A may be applied to a pipe Por to any fiat or other type of surface. As illustrated in FIGS. 1 and2, the object to be heated is a pipe P and the heat conductor element His a pair of electrical heating wires and 21 which are of coursesuitably connected to a source of electrical current 'for resistancetype heating. In other instances, the heat In any event, the heating orcooling element or elements H are embedded in the heat transfer material12 by pressing the heat transfer applicator downwardly on top of suchelement or elements H to embed or substantially cover the element orelements H. In that way, all air spaces are eliminated around theelement H and a very efficient heat transfer is obtained. The presenceof the channel member 10 prevents any shifting of the heat transfermaterial 12 and assures its proper application around the element orelements H.

When the channel member 10 is thus in place on the pipe P or otherobject, the channel member 10 is secured in place by the clamping bandsor straps 30 or other suitable securing means. With such construction,the heating or cooling elements H can be immediately used, whether thematerial 12 is thermosetting or non-hardening, the channel 10 serves toprevent harmful movement of the elements H and the material 12 relativeto each other and the pipe P. When the heat transfer material 12 is athermosetting material, it may be hardened by transmitting heat throughthe element or elements H so that the heat transfer material 12 becomesa relatively hard material permanently locking the electrical wires orother heating elements H to the pipe P. In this connection, it should benoted that when the heat conductor elements H are electrical wires 20and 21, the channel member 10 is of particular importance since itprevents any movement of the heating elements when they expand due tothe resistance heating. In other words, if the electrical wires areplaced in a heat transfer material, or are simply covered by a heattransfer material, and allowed to heat up, they will expand prior to thetime the heat transfer material has hardened and this will result inlocal areas of expansion, causing air spaces and consequent over-heatingof the wires at such air spaces. The presence of the channel member 10and the securing bands 30 prevents any such over-heating due to localareas of expansion of the heater wires.

Also, it should be noted that use of the channel member 10 provides aprefabricated applicator which assures an even distribution of the heattransfer material 12 with respect to the heating element or elements Hso as to avoid leaving any air gaps or uneven areas around the heatingelement or elements H to again assure against the over-heating atlocalized areas which might otherwise occur.

In FIGS. 4, 5, 6 and 7, different shaped channel members 110, 210, 310and 410 are illustrated, each of which has its inner channel filled witha heat transfer material 12. The modifications of FIGS. 4-7 areillustrated to make it clear that the invention is not limited to anyparticular shape of the channel member 10 since each of themodifications of FIGS. 4-7 may be employed in the heat transferapparatus A instead of the semi-cylindrical channel member 10 of FIGS.1-3.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof and various changes in the size,shape and materials, as well as in the details of the illustratedconstruction, may be made within the scope of the appended claimswithout departing from the spirit of the invention.

What is claimed is:

1. Heat transfer apparatus, comprising:

(a) a pipe adapted to be heated;

(b) a channel member having a pair of longitudinally extending edges anda longitudinal cavity formed between said edges;

(c) a heat conductor element extending longitudinally within saidcavity;

'(d) heat transfer material disposed and filling all of the space insaid cavity except for the portion occupied by said heat conductorelement;

(e) said heat transfer material and said channel member being preformedand disposed as a unit on said (f) said longitudinal edges of saidchannel member engaging the curved longitudinal surface of said pipe;

(g) said heat transfer material including a heat conducting agent forincreasing the heat transfer between said heat conductor element andsaid pipe as compared to the heat transfer with the heat conductorelement alone; and

(h) a plurality of clamping bands encircling said pipe and said channelmember to hold said longitudinal edges of said channel member in contactwith the external curved surface of said pipe for preventing theformation of air gaps in the heat transfer material between the heatconductor element and the pipe and for maintaining an increased heattransfer between the heat conductor element and the pipe.

2. The structure set forth in claim 1, wherein:

(a) said heat conductor element includes a pair of electric resistanceheating wires.

6 References Cited UNITED STATES PATENTS 2/1917 Heller 219-436 5/1922Stranszky 219-544 X 3/1928 Hynes 219-535 X 5/1942 Place 219-544 X 1/1957 Palmer. 4 11/1957 Fulham 219-535 X 5/1961 Brown et al 219-535 X10/1965 Indoe 219-535 X FOREIGN PATENTS 7/1921 Sweden.

ANTHONY BARTIS, Primary Examiner.

1. HEAT TRANSFER APPARATUS, COMPRISING: (A) A PIPE ADAPTED TO BE HEATED;(B) A CHANNEL MEMBER HAVING A PAIR OF LONGITUDINALLY EXTENDING EDGES ANDA LONGITUDINAL CAVITY FORMED BETWEEN SAID EDGES; (C) A HEAT CONDUCTORELEMENT EXTENDING LONGITUDINALLY WITHIN SAID CAVITY; (D) HEAT TRANSFERMATERIAL DISPOSED AND FILLING ALL OF THE SPACE IN SAID CAVITY EXCEPT FORTHE PORTION OCCUPIED BY SAID HEAT CONDUCTOR ELEMENT; (E) SAID HEATTRANSFER MATERIAL AND SAID CHANNEL MEMBER BEING PREFORMED AND DISPOSEDAS A UNIT ON SAID PIPE; (F) SAID LONGITUDINAL EDGES OF SAID CHANNELMEMBER ENGAGING THE CURVED LONGITUDINAL SURFACE OF SAID PIPE; (G) SAIDHEAT TRANSFER MATERIAL INCLUDING A HEAT CONDUCTING AGENT FOR INCREASINGTHE HEAT TRANSFER BETWEEN SAID HEAT CONDUCTOR ELEMENT AND SAID PIPE ASCOMPARED TO THE HEAT TRANSFER WITH THE HEAT CONDUCTOR ELEMENT ALONE; AND(H) A PLURALITY OF CLAMPING BANDS ENCIRCLING SAID PIPE AND SAID CHANNELMEMBER TO HOLD SAID LONGITUDINAL EDGES OF SAID CHANNEL MEMBER IN CONTACTWITH THE EXTERNAL CURVED SURFACE OF SAID PIPE FOR PREVENTING THEFORMATION OF AIR GAPS IN THE HEAT TRANSFER MATERIAL BETWEEN THE HEATCONDUCTOR ELEMENT AND THE PIPE AND FOR MAINTAINING AN INCREASED HEATTRANSFER BETWEEN THE HEAT CONDUCTOR ELEMENT AND THE PIPE.